共查询到16条相似文献,搜索用时 406 毫秒
1.
对Q345R钢在湿硫化氢环境中预腐蚀低周疲劳性能进行了研究,以硫化氢溶液的浓度和预腐蚀时间为环境因素.低周疲劳试验在MTS-809疲劳试验机上进行,对各试验组的结果数据进行回归分析,得到各试验组环境下Q345R钢的循环应力-应变曲线、应变-寿命曲线等低周疲劳特性.不同试验环境下的预腐蚀低周疲劳结果表明,材料循环应力应变响应特性不受环境因素影响,为循环硬化特性;预腐蚀时间因素对材料低周疲劳寿命的影响比硫化氢溶液的浓度因素显著.试样断口为典型的低周疲劳断裂形貌,裂纹扩展阶段为脆性准解理断裂特征. 相似文献
2.
对2D70铝合金在试验室空气、湿空气、盐雾及盐雾+SO2四种环境下进行低周疲劳试验,将得到的四种环境下的循环δ-ε曲线及应变一寿命曲线分别进行对比,得出结论:相同应变下,2D70铝合金随腐蚀环境增强,循环应力降低;相同应变下,2D70铝合金在盐雾及盐雾+SO2两种环境下低周疲劳寿命相近,并且随着腐蚀环境的增强,低周疲劳寿命降低。 相似文献
3.
对2D70铝合金在试验室空气、湿空气、盐雾及盐雾+SO四种环境下进行低周疲劳试验,对比四种环境下的循环σ-ε2曲线及应变-寿命曲线,得出结论:相同应变下,2D70铝合金随腐蚀环境增强,循环应力降低;相同应变下,2D70铝合金在盐雾及盐雾+SO两种环境下低周疲劳寿命相近,并且随着腐蚀环境的增强,低周疲劳寿命降低;腐蚀环境越强,材料疲劳损2伤程度越大。研究结果为预测飞机不同环境的低周疲劳寿命提供了参考,对飞机腐蚀防护及耐久性设计具有重要意义。 相似文献
4.
5.
基于低周疲劳裂纹扩展机制,假设裂纹尖端循环塑性区内应变分布服从HRR理论解,利用裂纹尖端锐化、钝化启裂低周疲劳裂纹扩展机制,结合Ramberg-Osgood循环应力应变曲线和Manson-Coffin疲劳寿命曲线等断裂力学理论,推导出一种新的低周疲劳裂纹扩展速率数学模型.与30Cr1Mo1V和St-4340的低周疲劳裂纹扩展速率试验数据进行对比,结果表明该低周疲劳裂纹扩展速率模型能够较好地预测材料的低周疲劳裂纹扩展速率. 相似文献
6.
7.
GH150合金叶片的疲劳性能 总被引:1,自引:0,他引:1
研究了高压压气机叶片用Ni基高温合金GH150的疲劳性能.试验方式分别为轴向拉伸和旋转弯曲疲劳.试验温度为500℃和600℃,试验按置信度90%和存活率50%进行.轴向拉伸和旋转弯曲疲劳性能试验Kt=1,应力状态分别为r=0.1和r=~1.用升降法求得500℃轴向拉伸疲劳107疲劳极限为481.8MPa,600℃疲劳极限为502MPa;500℃旋转弯曲疲劳107疲劳极限为418.57MPa,600℃为435.71MPa.轴向拉伸和旋转弯曲疲劳S-N曲线显示,随载荷应力的增加,疲劳循环次数呈减小趋势;在低应力长寿命区600℃的疲劳性能较500℃稍优.疲劳试样断口形貌照片显示,断口的源区、扩展区和最后瞬断区特征清晰;扩展区有明显的疲劳条带;瞬断区为韧性断裂. 相似文献
8.
15Cr14Co12Mo5Ni2齿轮钢的扭转疲劳特性及裂纹扩展行为 总被引:1,自引:0,他引:1
通过扭转疲劳试验,研究了15Cr14Co12Mo5Ni2钢的扭转疲劳断裂的裂纹扩展行为和夹杂物尺寸与扭转疲劳寿命之间的关系。得到了钢的扭转疲劳极限强度和[τ-N]曲线,15Cr14Co12Mo5Ni2钢的扭转疲劳极限强度为350 MPa,扭转疲劳寿命分散度较大。通过断口观察,发现15Cr14Co12Mo5Ni2钢的疲劳破坏模式以表面破坏和近表面破坏为主,主要由氧化物夹杂引起。通过计算应力强度因子[ΔK]和裂纹扩展门槛值[ΔKth]分析15Cr14Co12Mo5Ni2钢的疲劳裂纹扩展的断裂力学条件,试验钢在断裂过程中受载荷情况为,II型载荷—I型载荷—II型载荷—I+II型载荷,分别对应起裂源区、纤维区、疲劳裂纹扩展区和瞬断区;当有大裂纹产生时,则不会产生纤维区,受载荷情况则为:II型载荷—I+II型载荷。通过公式推导和数据拟合得到夹杂物尺寸和15Cr14Co12Mo5Ni2钢扭转疲劳寿命的关系,发现随着夹杂物尺寸减小,钢的[τ-N]曲线向高寿命区移动。当引起裂纹萌生的夹杂物尺寸小于5 μm时,在350 MPa应力下,15Cr14Co12Mo5Ni2钢的扭转疲劳寿命超过107循环周次。 相似文献
9.
10.
11.
12.
L. F. Van Swam R. M. Pelloux N. J. Grant 《Metallurgical and Materials Transactions A》1975,6(1):45-54
The cyclic stress-strain curves, the low cycle and high cycle fatigue lives and the fatigue crack growth rates of annealed
(1 h 820°C) and aged (3 h 480°C) maraging steel 300 were determined. Incremental step testing and stable hysteresis loop tip
measurements were used to determine the cyclic σ-ε curves. Both annealed and aged maraging steels were found to cyclically soften at room temperature over a plastic strain
range from 0.1 to 20 pct. The S-N curves were determined from 10 to 107 cycles to failure by plastic strain controlled low cycle fatigue tests performed in air and load controlled high cycle fatigue
tests performed in dry argon. The test results compared very well with the theoretical lifetime predictions derived from Tomkins’
theory. Fatigue crack growth rates were measured in air and dry argon for the annealed and aged alloys. Crack growth rates
of annealed maraging steel were found to be equal to those of aged maraging steel at rates between 10-7 and 10-5 in./cycle. A significant difference in crack growth rates in the two environments was found at low stress intensity factor
ranges, indicating a high susceptibility to corrosion fatigue in the presence of water vapor. The mechanisms of cyclic softening
in the two alloys are discussed in terms of dislocations rearrangement in the annealed alloy and dislocation-precipitate interactions
in the aged alloy. 相似文献
13.
Hot bulk forming tools are subject to high thermal and mechanical alternating loads which can induce the formation of fatigue cracks in the highly stressed regions of the tool. It this way, premature tool failure occurs with which increased tool costs are associated. It is therefore vitally important to calculate the tool life output during the process design to improve the efficiency. Thermomechanical fatigue tests using the hot‐working tool steel X38CrMoV5‐3 are carried out as the basis for service life predictions in order to characterise the material behaviour subject to cyclic loading. In the tests, the thermal and mechanical loads operating in the tool steel during a forging process are reproduced. In this way, a strain controlled S‐N curve is determined for a specific temperature interval by varying the applied mechanical load. Thus it is possible to consider the damage mechanisms in the material, which operate during the forming process, for computing the service life. Based on the experimentally determined strain controlled S‐N curve, the computation of a fatigue failure is carried out for a practical example with tool fracture. By comparing the material's experimentally determined load carrying capacity with the loading computed by employing the elastic‐plastic material behaviour, the number of forging cycles is ascertained up to incipient cracking. The simulation model introduced here permits an improved prediction of the fatigue crack formation by integrating the cyclic material behaviour subject to similar conditions found in the forging process. 相似文献
14.
D. Eylon J. A. Hall C. M. Pierce D. L. Ruckle 《Metallurgical and Materials Transactions A》1976,7(11):1817-1826
To establish correlations between microstructure and mechanical properties for the Ti-ll alloy, twelve different combinations
of hot die forging and heat treatment, in the a + 8 and Β phase regions, were investigated. The resulting heat treated forgings
were classified into four distinct categories based on their microstructural appearance. The room temperature tensile, post-creep
tensile, fracture toughness and fatigue crack propagation properties were measured along with creep and low cycle fatigue
at 566‡C. The creep, tensile, fatigue crack propagation and fracture toughness properties, grouped in a manner similar to
the microstructural categories. The fracture appearance and behavior of the cracks during propagation in fatigue and in fracture
toughness tests were examined, and correlations with the microstructure discussed. In the case of the fully transformed acicular
microstructure, it was found that the size and the orientation of colonies of similarly aligned α needles are dominant factors
in the crack behavior.
Formerly a National Research Council Associate, Air Force Materials Laboratory
Formerly with AFML 相似文献
15.
D. Eylon J. A. Hall C. M. Pierce D. L. Ruckle 《Metallurgical and Materials Transactions A》1976,7(12):1817-1826
To establish correlations between microstructure and mechanical properties for the Till alloy, twelve different combinations
of hot die forging and heat treatment, in the α+β and β phase regions, were investigated. The resulting heat treated forgings
were classified into four distinct categories based on their microstructural appearance. The room temperature tensile, post-creep
tensile, fracture toughness and fatigue crack propagation properties were measured along with creep and low cycle fatigue
at 566°C. The creep, tensile, fatigue crack propagation and fracture toughness properties, grouped in a manner similar to
the microstructural categories. The fracture appearance and behavior of the cracks during propagation in fatigue and in fracture
toughness tests were examined, and correlations with the microstructure discussed. In the case of the fully transformed acicular
microstructure, it was found that the size and the orientation of colonies of similarly aligned α needles are dominant factors
in the crack behavior. 相似文献
16.
Xinqiang Wu Yasuyuki Katada In S. Kim Sang G. Lee 《Metallurgical and Materials Transactions A》2004,35(5):1477-1486
The temperature- and strain-rate-dependent tensile behavior of hydrogen-charged low-alloy pressure vessel steel ASTM A508
C1.3 has been investigated. The fatigue crack initiation and propagation behavior of the steel in high-temperature water environments
has also been evaluated. It was found that hydrogen played significant roles in both tensile and cyclic deformation processes,
especially in the temperature and strain-rate region of dynamic strain aging (DSA). The presence of hydrogen resulted in a
distinct softening in tensile strength and a certain loss in tensile ductility in the DSA region. Remarkable degradation in
fatigue crack initiation and propagation resistance in high-temperature water environments was observed in the DSA strain-rate
region. Typical hydrogen-induced cracking features also appeared on the corresponding fatigue fracture surfaces. The interactions
between hydrogen and DSA in tensile and cyclic deformation processes are discussed as well as their combined effects on the
environmentally assisted cracking (EAC) mechanism of pressure vessel steels in high-temperature water environments. 相似文献